Extreme ultraviolet mask absorber materials

ABSTRACT

Extreme ultraviolet (EUV) mask blanks, methods for their manufacture and production systems therefor are disclosed. The EUV mask blanks comprise a substrate; a multilayer stack of reflective layers on the substrate; a capping layer on the multilayer stack of reflecting layers; and an absorber layer on the capping layer, the absorber layer made from carbon and antimony.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/799,320, filed Jan. 31, 2019, the entire disclosure of which ishereby incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to extreme ultravioletlithography, and more particularly extreme ultraviolet mask blanks withan alloy absorber and methods of manufacture.

BACKGROUND

Extreme ultraviolet (EUV) lithography, also known as soft x-rayprojection lithography, can be used for the manufacture of 0.0135 micronand smaller minimum feature size semiconductor devices. However, extremeultraviolet light, which is generally in the 5 to 100 nanometerwavelength range, is strongly absorbed in virtually all materials. Forthat reason, extreme ultraviolet systems work by reflection rather thanby transmission of light. Through the use of a series of mirrors, orlens elements, and a reflective element, or mask blank, coated with anon-reflective absorber mask pattern, the patterned actinic light isreflected onto a resist-coated semiconductor substrate.

The lens elements and mask blanks of extreme ultraviolet lithographysystems are coated with reflective multilayer coatings of materials suchas molybdenum and silicon. Reflection values of approximately 65% perlens element, or mask blank, have been obtained by using substrates thatare coated with multilayer coatings that strongly reflect light withinan extremely narrow ultraviolet bandpass, for example, 12.5 to 14.5nanometer bandpass for 13.5 nanometer ultraviolet light.

FIG. 1 shows a conventional EUV reflective mask 10, which is formed froman EUV mask blank, which includes a reflective multilayer stack 12 on asubstrate 14, which reflects EUV radiation at unmasked portions by Bragginterference. Masked (non-reflective) areas 16 of the conventional EUVreflective mask 10 are formed by etching buffer layer 18 and absorbinglayer 20. The absorbing layer typically has a thickness in a range of 51nm to 77 nm. A capping layer 22 is formed over the reflective multilayerstack 12 and protects the reflective multilayer stack 12 during theetching process. As will be discussed further below, EUV mask blanks aremade of on a low thermal expansion material substrate coated withmultilayers, a capping layer and an absorbing layer, which is thenetched to provide the masked (non-reflective) areas 16 and reflectiveareas 24.

The International Technology Roadmap for Semiconductors (ITRS) specifiesa node's overlay requirement as some percentage of a technology'sminimum half-pitch feature size. Due to the impact on image placementand overlay errors inherent in all reflective lithography systems, EUVreflective masks will need to adhere to more precise flatnessspecifications for future production. Additionally, EUV blanks have avery low tolerance to defects on the working area of the blank.Furthermore, while the absorbing layer's role is to absorb light, thereis also a phase shift effect due to the difference between the absorberlayer's index of refraction and vacuum's index of refraction (n=1), andthis phase shift that accounts for the 3D mask effects. There is a needto provide EUV mask blanks having a thinner absorber to mitigate 3D maskeffects.

SUMMARY

One or more embodiments of the disclosure are directed to a method ofmanufacturing an extreme ultraviolet (EUV) mask blank comprising formingon a substrate a multilayer stack which reflects EUV radiation, themultilayer stack comprising a plurality of reflective layer pairs;forming a capping layer on the multilayer stack; and forming an absorberlayer on the capping layer, the absorber layer comprising an alloy ofcarbon and antimony.

Additional embodiments of the disclosure are directed to an EUV maskblank comprising a substrate; a multilayer stack which reflects EUVradiation, the multilayer stack comprising a plurality of reflectivelayer; a capping layer on the multilayer stack of reflecting layers; andan absorber layer comprising an alloy of carbon and antimony.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 schematically illustrates a background art EUV reflective maskemploying a conventional absorber;

FIG. 2 schematically illustrates an embodiment of an extreme ultravioletlithography system;

FIG. 3 illustrates an embodiment of an extreme ultraviolet reflectiveelement production system;

FIG. 4 illustrates an embodiment of an extreme ultraviolet reflectiveelement such as an EUV mask blank;

FIG. 5 illustrates an embodiment of an extreme ultraviolet reflectiveelement such as an EUV mask blank; and

FIG. 6 illustrates an embodiment of a multi-cathode physical depositionchamber.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

The term “horizontal” as used herein is defined as a plane parallel tothe plane or surface of a mask blank, regardless of its orientation. Theterm “vertical” refers to a direction perpendicular to the horizontal asjust defined. Terms, such as “above”, “below”, “bottom”, “top”, “side”(as in “sidewall”), “higher”, “lower”, “upper”, “over”, and “under”, aredefined with respect to the horizontal plane, as shown in the figures.

The term “on” indicates that there is direct contact between elements.The term “directly on” indicates that there is direct contact betweenelements with no intervening elements.

Those skilled in the art will understand that the use of ordinals suchas “first” and “second” to describe process regions do not imply aspecific location within the processing chamber, or order of exposurewithin the processing chamber.

As used in this specification and the appended claims, the term“substrate” refers to a surface, or portion of a surface, upon which aprocess acts. It will also be understood by those skilled in the artthat reference to a substrate can refer to only a portion of thesubstrate, unless the context clearly indicates otherwise. Additionally,reference to depositing on a substrate can mean both a bare substrateand a substrate with one or more films or features deposited or formedthereon.

Referring now to FIG. 2, an exemplary embodiment of an extremeultraviolet lithography system 100 is shown. The extreme ultravioletlithography system 100 includes an extreme ultraviolet light source 102for producing extreme ultraviolet light 112, a set of reflectiveelements, and a target wafer 110. The reflective elements include acondenser 104, an EUV reflective mask 106, an optical reduction assembly108, a mask blank, a mirror, or a combination thereof.

The extreme ultraviolet light source 102 generates the extremeultraviolet light 112. The extreme ultraviolet light 112 iselectromagnetic radiation having a wavelength in a range of 5 to 50nanometers (nm). For example, the extreme ultraviolet light source 102includes a laser, a laser produced plasma, a discharge produced plasma,a free-electron laser, synchrotron radiation, or a combination thereof.

The extreme ultraviolet light source 102 generates the extremeultraviolet light 112 having a variety of characteristics. The extremeultraviolet light source 102 produces broadband extreme ultravioletradiation over a range of wavelengths. For example, the extremeultraviolet light source 102 generates the extreme ultraviolet light 112having wavelengths ranging from 5 to 50 nm.

In one or more embodiments, the extreme ultraviolet light source 102produces the extreme ultraviolet light 112 having a narrow bandwidth.For example, the extreme ultraviolet light source 102 generates theextreme ultraviolet light 112 at 13.5 nm. The center of the wavelengthpeak is 13.5 nm.

The condenser 104 is an optical unit for reflecting and focusing theextreme ultraviolet light 112. The condenser 104 reflects andconcentrates the extreme ultraviolet light 112 from the extremeultraviolet light source 102 to illuminate the EUV reflective mask 106.

Although the condenser 104 is shown as a single element, it isunderstood that the condenser 104 can include one or more reflectiveelements such as concave mirrors, convex mirrors, flat mirrors, or acombination thereof, for reflecting and concentrating the extremeultraviolet light 112. For example, the condenser 104 can be a singleconcave mirror or an optical assembly having convex, concave, and flatoptical elements.

The EUV reflective mask 106 is an extreme ultraviolet reflective elementhaving a mask pattern 114. The EUV reflective mask 106 creates alithographic pattern to form a circuitry layout to be formed on thetarget wafer 110. The EUV reflective mask 106 reflects the extremeultraviolet light 112. The mask pattern 114 defines a portion of acircuitry layout.

The optical reduction assembly 108 is an optical unit for reducing theimage of the mask pattern 114. The reflection of the extreme ultravioletlight 112 from the EUV reflective mask 106 is reduced by the opticalreduction assembly 108 and reflected on to the target wafer 110. Theoptical reduction assembly 108 can include mirrors and other opticalelements to reduce the size of the image of the mask pattern 114. Forexample, the optical reduction assembly 108 can include concave mirrorsfor reflecting and focusing the extreme ultraviolet light 112.

The optical reduction assembly 108 reduces the size of the image of themask pattern 114 on the target wafer 110. For example, the mask pattern114 can be imaged at a 4:1 ratio by the optical reduction assembly 108on the target wafer 110 to form the circuitry represented by the maskpattern 114 on the target wafer 110. The extreme ultraviolet light 112can scan the EUV reflective mask 106 synchronously with the target wafer110 to form the mask pattern 114 on the target wafer 110.

Referring now to FIG. 3, an embodiment of of an extreme ultravioletreflective element production system 200 is shown. The extremeultraviolet reflective element includes a EUV mask blank 204, an extremeultraviolet mirror 205, or other reflective element such as an EUVreflective mask 106.

The extreme ultraviolet reflective element production system 200 canproduce mask blanks, mirrors, or other elements that reflect the extremeultraviolet light 112 of FIG. 2. The extreme ultraviolet reflectiveelement production system 200 fabricates the reflective elements byapplying thin coatings to source substrates 203.

The EUV mask blank 204 is a multilayered structure for forming the EUVreflective mask 106 of FIG. 2. The EUV mask blank 204 can be formedusing semiconductor fabrication techniques. The EUV reflective mask 106can have the mask pattern 114 of FIG. 2 formed on the EUV mask blank 204by etching and other processes.

The extreme ultraviolet mirror 205 is a multilayered structurereflective in a range of extreme ultraviolet light. The extremeultraviolet mirror 205 can be formed using semiconductor fabricationtechniques. The EUV mask blank 204 and the extreme ultraviolet mirror205 can be similar structures with respect to the layers formed on eachelement, however, the extreme ultraviolet mirror 205 does not have themask pattern 114.

The reflective elements are efficient reflectors of the extremeultraviolet light 112. In an embodiment, the EUV mask blank 204 and theextreme ultraviolet mirror 205 has an extreme ultraviolet reflectivityof greater than 60%. The reflective elements are efficient if theyreflect more than 60% of the extreme ultraviolet light 112.

The extreme ultraviolet reflective element production system 200includes a wafer loading and carrier handling system 202 into which thesource substrates 203 are loaded and from which the reflective elementsare unloaded. An atmospheric handling system 206 provides access to awafer handling vacuum chamber 208. The wafer loading and carrierhandling system 202 can include substrate transport boxes, loadlocks,and other components to transfer a substrate from atmosphere to vacuuminside the system. Because the EUV mask blank 204 is used to formdevices at a very small scale, the source substrates 203 and the EUVmask blank 204 are processed in a vacuum system to prevent contaminationand other defects.

The wafer handling vacuum chamber 208 can contain two vacuum chambers, afirst vacuum chamber 210 and a second vacuum chamber 212. The firstvacuum chamber 210 includes a first wafer handling system 214 and thesecond vacuum chamber 212 includes a second wafer handling system 216.Although the wafer handling vacuum chamber 208 is described with twovacuum chambers, it is understood that the system can have any number ofvacuum chambers.

The wafer handling vacuum chamber 208 can have a plurality of portsaround its periphery for attachment of various other systems. The firstvacuum chamber 210 has a degas system 218, a first physical vapordeposition system 220, a second physical vapor deposition system 222,and a pre-clean system 224. The degas system 218 is for thermallydesorbing moisture from the substrates. The pre-clean system 224 is forcleaning the surfaces of the wafers, mask blanks, mirrors, or otheroptical components.

The physical vapor deposition systems, such as the first physical vapordeposition system 220 and the second physical vapor deposition system222, can be used to form thin films of conductive materials on thesource substrates 203. For example, the physical vapor depositionsystems can include vacuum deposition system such as magnetronsputtering systems, ion sputtering systems, pulsed laser deposition,cathode arc deposition, or a combination thereof. The physical vapordeposition systems, such as the magnetron sputtering system, form thinlayers on the source substrates 203 including the layers of silicon,metals, alloys, compounds, or a combination thereof.

The physical vapor deposition system forms reflective layers, cappinglayers, and absorber layers. For example, the physical vapor depositionsystems can form layers of silicon, molybdenum, titanium oxide, titaniumdioxide, ruthenium oxide, niobium oxide, ruthenium tungsten, rutheniummolybdenum, ruthenium niobium, chromium, antimony, nitrides, compounds,or a combination thereof. Although some compounds are described as anoxide, it is understood that the compounds can include oxides, dioxides,atomic mixtures having oxygen atoms, or a combination thereof.

The second vacuum chamber 212 has a first multi-cathode source 226, achemical vapor deposition system 228, a cure chamber 230, and anultra-smooth deposition chamber 232 connected to it. For example, thechemical vapor deposition system 228 can include a flowable chemicalvapor deposition system (FCVD), a plasma assisted chemical vapordeposition system (CVD), an aerosol assisted CVD, a hot filament CVDsystem, or a similar system. In another example, the chemical vapordeposition system 228, the cure chamber 230, and the ultra-smoothdeposition chamber 232 can be in a separate system from the extremeultraviolet reflective element production system 200.

The chemical vapor deposition system 228 can form thin films of materialon the source substrates 203. For example, the chemical vapor depositionsystem 228 can be used to form layers of materials on the sourcesubstrates 203 including mono-crystalline layers, polycrystallinelayers, amorphous layers, epitaxial layers, or a combination thereof.The chemical vapor deposition system 228 can form layers of silicon,silicon oxides, silicon oxycarbide, carbon, tungsten, silicon carbide,silicon nitride, titanium nitride, metals, alloys, and other materialssuitable for chemical vapor deposition. For example, the chemical vapordeposition system can form planarization layers.

The first wafer handling system 214 is capable of moving the sourcesubstrates 203 between the atmospheric handling system 206 and thevarious systems around the periphery of the first vacuum chamber 210 ina continuous vacuum. The second wafer handling system 216 is capable ofmoving the source substrates 203 around the second vacuum chamber 212while maintaining the source substrates 203 in a continuous vacuum. Theextreme ultraviolet reflective element production system 200 cantransfer the source substrates 203 and the EUV mask blank 204 betweenthe first wafer handling system 214, the second wafer handling system216 in a continuous vacuum.

Referring now to FIG. 4, an embodiment of an extreme ultravioletreflective element 302 is shown. In one or more embodiments, the extremeultraviolet reflective element 302 is the EUV mask blank 204 of FIG. 3or the extreme ultraviolet mirror 205 of FIG. 3. The EUV mask blank 204and the extreme ultraviolet mirror 205 are structures for reflecting theextreme ultraviolet light 112 of FIG. 2. The EUV mask blank 204 can beused to form the EUV reflective mask 106 shown in FIG. 2.

The extreme ultraviolet reflective element 302 includes a substrate 304,a multilayer stack 306 of reflective layers, and a capping layer 308. Inone or more embodiments, the extreme ultraviolet mirror 205 is used toform reflecting structures for use in the condenser 104 of FIG. 2 or theoptical reduction assembly 108 of FIG. 2.

The extreme ultraviolet reflective element 302, which can be a EUV maskblank 204, includes the substrate 304, the multilayer stack 306 ofreflective layers, the capping layer 308, and an absorber layer 310. Theextreme ultraviolet reflective element 302 can be a EUV mask blank 204,which is used to form the EUV reflective mask 106 of FIG. 2 bypatterning the absorber layer 310 with the layout of the circuitryrequired.

In the following sections, the term for the EUV mask blank 204 is usedinterchangeably with the term of the extreme ultraviolet mirror 205 forsimplicity. In one or more embodiments, the EUV mask blank 204 includesthe components of the extreme ultraviolet mirror 205 with the absorberlayer 310 added in addition to form the mask pattern 114 of FIG. 2.

The EUV mask blank 204 is an optically flat structure used for formingthe EUV reflective mask 106 having the mask pattern 114. In one or moreembodiments, the reflective surface of the EUV mask blank 204 forms aflat focal plane for reflecting the incident light, such as the extremeultraviolet light 112 of FIG. 2.

The substrate 304 is an element for providing structural support to theextreme ultraviolet reflective element 302. In one or more embodiments,the substrate 304 is made from a material having a low coefficient ofthermal expansion (CTE) to provide stability during temperature changes.In one or more embodiments, the substrate 304 has properties such asstability against mechanical cycling, thermal cycling, crystalformation, or a combination thereof. The substrate 304 according to oneor more embodiments is formed from a material such as silicon, glass,oxides, ceramics, glass ceramics, or a combination thereof.

The multilayer stack 306 is a structure that is reflective to theextreme ultraviolet light 112. The multilayer stack 306 includesalternating reflective layers of a first reflective layer 312 and asecond reflective layer 314.

The first reflective layer 312 and the second reflective layer 314 forma reflective pair 316 of FIG. 4. In a non-limiting embodiment, themultilayer stack 306 includes a range of 20-60 of the reflective pairs316 for a total of up to 120 reflective layers.

The first reflective layer 312 and the second reflective layer 314 canbe formed from a variety of materials. In an embodiment, the firstreflective layer 312 and the second reflective layer 314 are formed fromsilicon and molybdenum, respectively. Although the layers are shown assilicon and molybdenum, it is understood that the alternating layers canbe formed from other materials or have other internal structures.

The first reflective layer 312 and the second reflective layer 314 canhave a variety of structures. In an embodiment, both the firstreflective layer 312 and the second reflective layer 314 are formed witha single layer, multiple layers, a divided layer structure, non-uniformstructures, or a combination thereof.

Because most materials absorb light at extreme ultraviolet wavelengths,the optical elements used are reflective instead of the transmissive asused in other lithography systems. The multilayer stack 306 forms areflective structure by having alternating thin layers of materials withdifferent optical properties to create a Bragg reflector or mirror.

In an embodiment, each of the alternating layers has dissimilar opticalconstants for the extreme ultraviolet light 112. The alternating layersprovide a resonant reflectivity when the period of the thickness of thealternating layers is one half the wavelength of the extreme ultravioletlight 112. In an embodiment, for the extreme ultraviolet light 112 at awavelength of 13 nm, the alternating layers are about 6.5 nm thick. Itis understood that the sizes and dimensions provided are within normalengineering tolerances for typical elements.

The multilayer stack 306 can be formed in a variety of ways. In anembodiment, the first reflective layer 312 and the second reflectivelayer 314 are formed with magnetron sputtering, ion sputtering systems,pulsed laser deposition, cathode arc deposition, or a combinationthereof.

In an illustrative embodiment, the multilayer stack 306 is formed usinga physical vapor deposition technique, such as magnetron sputtering. Inan embodiment, the first reflective layer 312 and the second reflectivelayer 314 of the multilayer stack 306 have the characteristics of beingformed by the magnetron sputtering technique including precisethickness, low roughness, and clean interfaces between the layers. In anembodiment, the first reflective layer 312 and the second reflectivelayer 314 of the multilayer stack 306 have the characteristics of beingformed by the physical vapor deposition including precise thickness, lowroughness, and clean interfaces between the layers.

The physical dimensions of the layers of the multilayer stack 306 formedusing the physical vapor deposition technique can be preciselycontrolled to increase reflectivity. In an embodiment, the firstreflective layer 312, such as a layer of silicon, has a thickness of 4.1nm. The second reflective layer 314, such as a layer of molybdenum, hasa thickness of 2.8 nm. The thickness of the layers dictates the peakreflectivity wavelength of the extreme ultraviolet reflective element.If the thickness of the layers is incorrect, the reflectivity at thedesired wavelength 13.5 nm can be reduced.

In an embodiment, the multilayer stack 306 has a reflectivity of greaterthan 60%. In an embodiment, the multilayer stack 306 formed usingphysical vapor deposition has a reflectivity in a range of 66%-67%. Inone or more embodiments, forming the capping layer 308 over themultilayer stack 306 formed with harder materials improves reflectivity.In some embodiments, reflectivity greater than 70% is achieved using lowroughness layers, clean interfaces between layers, improved layermaterials, or a combination thereof.

In one or more embodiments, the capping layer 308 is a protective layerallowing the transmission of the extreme ultraviolet light 112. In anembodiment, the capping layer 308 is formed directly on the multilayerstack 306. In one or more embodiments, the capping layer 308 protectsthe multilayer stack 306 from contaminants and mechanical damage. In oneembodiment, the multilayer stack 306 is sensitive to contamination byoxygen, carbon, hydrocarbons, or a combination thereof. The cappinglayer 308 according to an embodiment interacts with the contaminants toneutralize them.

In one or more embodiments, the capping layer 308 is an opticallyuniform structure that is transparent to the extreme ultraviolet light112. The extreme ultraviolet light 112 passes through the capping layer308 to reflect off of the multilayer stack 306. In one or moreembodiments, the capping layer 308 has a total reflectivity loss of 1%to 2%. In one or more embodiments, each of the different materials has adifferent reflectivity loss depending on thickness, but all of them willbe in a range of 1% to 2%.

In one or more embodiments, the capping layer 308 has a smooth surface.For example, the surface of the capping layer 308 can have a roughnessof less than 0.2 nm RMS (root mean square measure). In another example,the surface of the capping layer 308 has a roughness of 0.08 nm RMS fora length in a range of 1/100 nm and 1/1 μm. The RMS roughness will varydepending on the range it is measured over. For the specific range of100 nm to 1 micron that roughness is 0.08 nm or less. Over a largerrange the roughness will be higher.

The capping layer 308 can be formed in a variety of methods. In anembodiment, the capping layer 308 is formed on or directly on themultilayer stack 306 with magnetron sputtering, ion sputtering systems,ion beam deposition, electron beam evaporation, radio frequency (RF)sputtering, atomic layer deposition (ALD), pulsed laser deposition,cathode arc deposition, or a combination thereof. In one or moreembodiments, the capping layer 308 has the physical characteristics ofbeing formed by the magnetron sputtering technique including precisethickness, low roughness, and clean interfaces between the layers. In anembodiment, the capping layer 308 has the physical characteristics ofbeing formed by the physical vapor deposition including precisethickness, low roughness, and clean interfaces between the layers.

In one or more embodiments, the capping layer 308 is formed from avariety of materials having a hardness sufficient to resist erosionduring cleaning. In one embodiment, ruthenium is used as a capping layermaterial because it is a good etch stop and is relatively inert underthe operating conditions. However, it is understood that other materialscan be used to form the capping layer 308. In specific embodiments, thecapping layer 308 has a thickness in a range of 2.5 and 5.0 nm.

In one or more embodiments, the absorber layer 310 is a layer thatabsorbs the extreme ultraviolet light 112. In an embodiment, theabsorber layer 310 is used to form the pattern on the EUV reflectivemask 106 by providing areas that do not reflect the extreme ultravioletlight 112. The absorber layer 310, according to one or more embodiments,comprises a material having a high absorption coefficient for aparticular frequency of the extreme ultraviolet light 112, such as about13.5 nm. In an embodiment, the absorber layer 310 is formed directly onthe capping layer 308, and the absorber layer 310 is etched using aphotolithography process to form the pattern of the EUV reflective mask106.

According to one or more embodiments, the extreme ultraviolet reflectiveelement 302, such as the extreme ultraviolet mirror 205, is formed withthe substrate 304, the multilayer stack 306, and the capping layer 308.The extreme ultraviolet mirror 205 has an optically flat surface and canefficiently and uniformly reflect the extreme ultraviolet light 112.

According to one or more embodiments, the extreme ultraviolet reflectiveelement 302, such as the EUV mask blank 204, is formed with thesubstrate 304, the multilayer stack 306, the capping layer 308, and theabsorber layer 310. The mask blank 204 has an optically flat surface andcan efficiently and uniformly reflect the extreme ultraviolet light 112.In an embodiment, the mask pattern 114 is formed with the absorber layer310 of the EUV mask blank 204.

According to one or more embodiments, forming the absorber layer 310over the capping layer 308 increases reliability of the EUV reflectivemask 106. The capping layer 308 acts as an etch stop layer for theabsorber layer 310. When the mask pattern 114 of FIG. 2 is etched intothe absorber layer 310, the capping layer 308 beneath the absorber layer310 stops the etching action to protect the multilayer stack 306. In oneor more embodiments, the absorber layer 310 is etch selective to thecapping layer 308. In some embodiments, the capping layer 308 comprisesruthenium, and the absorber layer 310 is etch selective to ruthenium.

In an embodiment, the absorber layer 310 comprises an alloy of carbonand antimony. In some embodiments the absorber has a thickness of lessthan about 45 nm. In some embodiments, the absorber layer has athickness of less than about 45 nm, including less than about 40 nm,less than about 35 nm, less than about 30 nm, less than about 25 nm,less than about 20 nm, less than about 15 nm, less than about 10 nm,less than about 5 nm, less than about 1 nm, or less than about 0.5 nm.In other embodiments, the absorber layer 310 has a thickness in a rangeof about 0.5 nm to about 45 nm, including a range of about 1 nm to about44 nm, 1 nm to about 40 nm, and 15 nm to about 40 nm.

Without intending to be bound by theory, it is thought that an absorberlayer 310 having a thickness of less than about 45 nm advantageouslyresults in an absorber layer having a reflectively of less than about2%, reducing and mitigating 3D mask effects in the extreme ultraviolet(EUV) mask blank.

In an embodiment, the absorber layer 310 is made from an alloy of carbonand antimony. In one or more embodiments, the alloy of carbon andantimony comprises about 3.0 wt. % to about 27.1 wt. % carbon and about72.9 wt. % to about 97 wt. % antimony based upon the total weight of thealloy, for example, about 6.0 wt. % to about 15 wt. % carbon and about85 wt. % to about 94 wt. % antimony based upon the total weight of thealloy. In one or more embodiments, the alloy of carbon and antimonycomprises about 35 wt. % to about 55 wt. % carbon and about 45 wt. % toabout 65 wt. % antimony based upon the total weight of the alloy, forexample, about 45 wt. % to about 52 wt. % carbon and about 48 wt. % toabout 55 wt. % antimony based upon the total weight of the alloy. In oneor more embodiments, the alloy of carbon and antimony is amorphous.

In a specific embodiment, the alloy of carbon and antimony is antimonyrich alloy. As used herein, the term “antimony rich” means that there issignificantly more antimony in the alloy than carbon. For example, in aspecific embodiment, the alloy of carbon and antimony is an alloy whichcomprises about 3.0 wt. % to about 27.1 wt. % carbon and about 72.9 wt.% to about 97 wt. % antimony based upon the total weight of the alloy.In another specific embodiment, the alloy of carbon and antimony is analloy which comprises 6.0 wt. % to about 15 wt. % carbon and about 85wt. % to about 94 wt. % antimony based upon the total weight of thealloy. In one or more embodiments, the alloy of carbon and antimony isamorphous.

In one or more embodiments, the alloy of carbon and antimony comprises adopant. The dopant may be selected from one or more of nitrogen oroxygen. In an embodiment, the dopant comprises oxygen. In an alternativeembodiment, the dopant comprises nitrogen. In an embodiment, the dopantis present in the alloy in an amount in the range of about 0.1 wt. % toabout 5 wt. %, based on the weight of the alloy. In other embodiments,the dopant is present in the alloy in an amount of about 0.1 wt. %, 0.2wt. %, 0.3 wt. %, 0.4 wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %. 0.8 wt. %,0.9 wt. %, 1.0 wt. %, 1.1 wt. %, 1.2 wt. %, 1.3 wt. %, 1.4 wt. %, 1.5wt. %, 1.6 wt. %, 1.7 wt. %. 1.8 wt. %, 1.9 wt. %, 2.0 wt. % 2.1 wt. %,2.2 wt. %, 2.3 wt. %, 2.4 wt. %, 2.5 wt. %, 2.6 wt. %, 2.7 wt. %. 2.8wt. %, 2.9 wt. %, 3.0 wt. %, 3.1 wt. %, 3.2 wt. %, 3.3 wt. %, 3.4 wt. %,3.5 wt. %, 3.6 wt. %, 3.7 wt. %. 3.8 wt. %, 3.9 wt. %, 4.0 wt. %, 4.1wt. %, 4.2 wt. %, 4.3 wt. %, 4.4 wt. %, 4.5 wt. %, 4.6 wt. %, 4.7 wt. %.4.8 wt. %, 4.9 wt. %, or 5.0 wt. %.

In one or more embodiments, the alloy of the absorber layer is aco-sputtered alloy absorber material formed in a physical depositionchamber, which can provide much thinner absorber layer thickness (lessthan 30 nm) while achieving less than 2% reflectivity and suitable etchproperties. In one or more embodiments, the alloy of the absorber layercan be co-sputtered by gases selected from one or more of argon (Ar),oxygen (O₂), or nitrogen (N₂). In an embodiment, the alloy of theabsorber layer can be co-sputtered by a mixture of argon and oxygengases (Ar+O₂). In some embodiments, co-sputtering by a mixture of argonand oxygen forms and oxide of carbon and/or an oxide of antimony. Inother embodiments, co-sputtering by a mixture of argon and oxygen doesnot form an oxide of carbon or antimony. In an embodiment, the alloy ofthe absorber layer can be co-sputtered by a mixture of argon andnitrogen gases (Ar+N₂). In some embodiments, co-sputtering by a mixtureof argon and nitrogen forms a nitride of carbon and/or a nitride ofantimony. In other embodiments, co-sputtering by a mixture of argon andnitrogen does not form a nitride of carbon or antimony. In anembodiment, the alloy of the absorber layer can be co-sputtered by amixture of argon and oxygen and nitrogen gases (Ar+O₂+N₂). In someembodiments, co-sputtering by a mixture of argon and oxygen and nitrogenforms an oxide and/or nitride of carbon and/or an oxide and/or nitrideof antimony. In other embodiments, co-sputtering by a mixture of argonand oxygen and nitrogen does not form an oxide or a nitride of carbon orantimony. In an embodiment, the etch properties and/or other propertiesof the absorber layer can be tailored to specification by controllingthe alloy percentage(s), as discussed above. In an embodiment, the alloypercentage(s) can be precisely controlled by operating parameters suchvoltage, pressure, flow, etc., of the physical vapor deposition chamber.In an embodiment, a process gas is used to further modify the materialproperties, for example, N₂ gas is used to form nitrides of carbon andantimony.

In one or more embodiments, as used herein “co-sputtering” means thattwo targets, one target comprising carbon and the second targetcomprising antimony are sputtered at the same time using one or more gasselected from argon (Ar), oxygen (O₂), or nitrogen (N₂) to deposit/forman absorber layer comprising an alloy of carbon and antimony.

In other embodiments, the alloy of carbon and antimony can be depositedlayer by layer as a laminate of carbon and antimony layers using gasesselected from one or more of argon (Ar), oxygen (O₂), or nitrogen (N₂).In an embodiment, the alloy of the absorber layer can be deposited layerby layer as a laminate of carbon and antimony layers using a mixture ofargon and oxygen gases (Ar+O₂). In some embodiments, layer by layerdeposition using a mixture of argon and oxygen forms an oxide of carbonand/or an oxide of antimony. In other embodiments, layer by layerdeposition using a mixture of argon and oxygen does not form an oxide ofcarbon or antimony. In an embodiment, the alloy of the absorber layercan be deposited layer by layer as a laminate of carbon and antimonylayers using a mixture of argon and nitrogen gases (Ar+N₂). In someembodiments, layer by layer deposition using a mixture of argon andnitrogen forms a nitride of carbon and/or a nitride of antimony. Inother embodiments, layer by layer deposition using a mixture of argonand nitrogen does not form a nitride of carbon or antimony. In anembodiment, the alloy of the absorber layer can be deposited layer bylayer as a laminate of carbon and antimony layers using a mixture ofargon and oxygen and nitrogen gases (Ar+O₂+N₂). In some embodiments,layer by layer depositing using a mixture of argon and oxygen andnitrogen forms an oxide and/or nitride of carbon and/or an oxide and/ornitride of antimony. In other embodiments, layer by layer depositionusing a mixture of argon and oxygen and nitrogen does not form an oxideor a nitride of carbon or antimony.

In one or more embodiments, bulk targets of the alloy compositionsdescribed herein may be made, which can be sputtered by normalsputtering using gases selected from one or more of argon (Ar), oxygen(O₂), or nitrogen (N₂). In one or more embodiments, the alloy isdeposited using a bulk target having the same composition of the alloyand is sputtered using a gas selected from one or more of argon (Ar),oxygen (O₂), or nitrogen (N₂) to form the absorber layer. In anembodiment, the alloy of the absorber layer can be deposited using abulk target having the same composition of the alloy and is sputteredusing a mixture of argon and oxygen gases (Ar+O₂). In some embodiments,bulk target deposition using a mixture of argon and oxygen forms anoxide of carbon and/or an oxide of antimony. In other embodiments, bulktarget deposition using a mixture of argon and oxygen does not form anoxide of carbon or antimony. In an embodiment, the alloy of the absorberlayer can be deposited using a bulk target having the same compositionof the alloy and is sputtered using a mixture of argon and nitrogengases (Ar+N₂). In some embodiments, bulk target deposition using amixture of argon and nitrogen forms a nitride of carbon and/or a nitrideof antimony. In other embodiments, bulk target deposition using amixture of argon and nitrogen does not form a nitride of carbon orantimony. In an embodiment, the alloy of the absorber layer can bedeposited using a bulk target having the same composition of the alloyand is sputtered using a mixture of argon and oxygen and nitrogen gases(Ar+O₂+N₂). In some embodiments, bulk target depositing using a mixtureof argon and oxygen and nitrogen forms an oxide and/or nitride of carbonand/or an oxide and/or nitride of antimony. In other embodiments, bulktarget deposition using a mixture of argon and oxygen and nitrogen doesnot form an oxide or a nitride of carbon or antimony. In someembodiments, the alloy of carbon and antimony is doped with one of moreof nitrogen or oxygen in a range of from 0.1 wt. % to 5 wt. %.

The EUV mask blank can be made in a physical deposition chamber having afirst cathode comprising a first absorber material, a second cathodecomprising a second absorber material, a third cathode comprising athird absorber material, a fourth cathode comprising a fourth absorbermaterial, and a fifth cathode comprising a fifth absorber material,wherein the first absorber material, second absorber material, thirdabsorber material, fourth absorber material and fifth absorber materialsare different from each other, and each of the absorber materials havean extinction coefficient that is different from the other materials,and each of the absorber materials have an index of refraction that isdifferent from the other absorber materials.

Referring now to FIG. 5, an extreme ultraviolet mask blank 400 is shownas comprising a substrate 414, a multilayer stack of reflective layers412 on the substrate 414, the multilayer stack of reflective layers 412including a plurality of reflective layer pairs. In one or moreembodiments, the plurality of reflective layer pairs are made from amaterial selected from a molybdenum (Mo) containing material and silicon(Si) containing material. In some embodiments, the plurality ofreflective layer pairs comprise alternating layers of molybdenum andsilicon. The extreme ultraviolet mask blank 400 further includes acapping layer 422 on the multilayer stack of reflective layers 412, andthere is a multilayer stack 420 of absorber layers on the capping layer422. In one or more embodiment, the plurality of reflective layers 412are selected from a molybdenum (Mo) containing material and a silicon(Si) containing material and the capping layer 422 comprises ruthenium.

The multilayer stack 420 of absorber layers including includes aplurality of absorber layer pairs 420 a, 420 b, 420 c, 420 d, 420 e, 420f, each pair (420 a/420 b, 420 c/420 d, 420 e/420 f) comprising an alloyof carbon and antimony. In some embodiments, the alloy of carbon andantimony comprises about 3.0 wt. % to about 27.1 wt. % carbon and about72.9 wt. % to about 97 wt. % antimony, for example, about 6.0 wt. % toabout 15 wt. % carbon and about 85 wt. % to about 94 wt. % antimony, forexample, about 90.6 wt. % antimony and about 9.4 wt. % carbon. In otherembodiments, the alloy of carbon and antimony comprises about 35 wt. %to about 55 wt. % carbon and about 45 wt. % to about 65 wt. % antimony,for example, about 52 wt. % carbon and about 48 wt. % to about 55 wt. %antimony, for example, about 51.3 wt. % antimony and 48.7 wt. % carbon.

In one example, absorber layer 420 a is made from antimony and thematerial that forms absorber layer 420 b is carbon. Likewise, absorberlayer 420 c is made from antimony and the material that forms absorberlayer 420 d is carbon, and absorber layer 420 e is made from antimonymaterial and the material that forms absorber layer 420 f is carbon.

In one embodiment, the extreme ultraviolet mask blank 400 includes theplurality of reflective layers 412 selected from molybdenum (Mo)containing material and silicon (Si) containing material, for example,molybdenum (Mo) and silicon (Si). The absorber materials that are usedto form the absorber layers 420 a, 420 b, 420 c, 420 d, 420 e and 420 fare an alloy of carbon and antimony. In some embodiments, the alloy ofcarbon and antimony comprises about 3.0 wt. % to about 27.1 wt. % carbonand about 72.9 wt. % to about 97 wt. % antimony, for example, about 6.0wt. % to about 15 wt. % carbon and about 85 wt. % to about 94 wt. %antimony, for example, about 90.6 wt. % antimony and about 9.4 wt. %carbon. In other embodiments, the alloy of carbon and antimony comprisesabout 35 wt. % to about 55 wt. % carbon and about 45 wt. % to about 65wt. % antimony, for example, about 52 wt. % carbon and about 48 wt. % toabout 55 wt. % antimony, for example, about 51.3 wt. % antimony and 48.7wt. % carbon. In one or more embodiments, the alloy of carbon andantimony is amorphous.

In one or more embodiments, the absorber layer pairs 420 a/420 b, 420c/420 d, 420 e/420 f comprise a first layer (420 a, 420 c, 420 e)including an absorber material comprising an alloy of carbon andantimony and a second absorber layer (420 b, 420 d, 420 f) including anabsorber material including an alloy of carbon and antimony. In specificembodiments, the absorber layer pairs comprise a first layer (420 a, 420c, 420 e) including an alloy of carbon and antimony, the alloy of carbonand antimony selected from an alloy having about the alloy of carbon andantimony, and a second absorber layer (420 b, 420 d, 420 f) including anabsorber material including an alloy of carbon and antimony.

According to one or more embodiments, the absorber layer pairs comprisea first layer (420 a, 420 c, 420 e) and a second absorber layer (420 b,420 d, 420 f) each of the first absorber layers (420 a, 420 c, 420 e)and second absorber layer (420 b, 420 d, 420 f) have a thickness in arange of 0.1 nm and 10 nm, for example in a range of 1 nm and 5 nm, orin a range of 1 nm and 3 nm. In one or more specific embodiments, thethickness of the first layer 420 a is 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm,0.9 nm, 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm,1.8 nm, 1.9 nm, 2 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm, 2.5 nm, 2.6 nm,2.7 nm, 2.8 nm, 2.9 nm, 3 nm, 3.1 nm, 3.2 nm, 3.3 nm, 3.4 nm, 3.5 nm,3.6 nm, 3.7 nm, 3.8 nm, 3.9 nm, 4 nm, 4.1 nm, 4.2 nm, 4.3 nm, 4.4 nm,4.5 nm, 4.6 nm, 4.7 nm, 4.8 nm, 4.9 nm, and 5 nm. In one or moreembodiments, the thickness of the first absorber layer and secondabsorber layer of each pair is the same or different. For example, thefirst absorber layer and second absorber layer have a thickness suchthat there is a ratio of the first absorber layer thickness to secondabsorber layer thickness of 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1,4.5:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1,16:1, 17:1, 18:1, 19:1, or 20:1, which results in the first absorberlayer having a thickness that is equal to or greater than the secondabsorber layer thickness in each pair. Alternatively, the first absorberlayer and second absorber layer have a thickness such that there is aratio of the second absorber layer thickness to first absorber layerthickness of 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 6:1, 7:1,8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or20:1 which results in the second absorber layer having a thickness thatis equal to or greater than the first absorber layer thickness in eachpair.

According to one or more embodiments, the different absorber materialsand thickness of the absorber layers are selected so that extremeultraviolet light is absorbed due to absorbance and due to a phasechange caused by destructive interfere with light from the multilayerstack of reflective layers. While the embodiment shown in FIG. 5 showsthree absorber layer pairs, 420 a/420 b, 420 c/420 d and 420 e/420 f,the claims should not be limited to a particular number of absorberlayer pairs. According to one or more embodiments, the EUV mask blank400 can include in a range of 5 and 60 absorber layer pairs or in arange of 10 and 40 absorber layer pairs.

According to one or more embodiments, the absorber layers have athickness which provides less than 2% reflectivity and other etchproperties. A supply gas can be used to further modify the materialproperties of the absorber layers, for example, nitrogen (N₂) gas can beused to form nitrides of the materials provided above. The multilayerstack of absorber layers according to one or more embodiments is arepetitive pattern of individual thickness of different materials sothat the EUV light not only gets absorbed due to absorbance but by thephase change caused by multilayer absorber stack, which willdestructively interfere with light from multilayer stack of reflectivematerials beneath to provide better contrast.

Another aspect of the disclosure pertains to a method of manufacturingan extreme ultraviolet (EUV) mask blank comprising forming on asubstrate a multilayer stack of reflective layers on the substrate, themultilayer stack including a plurality of reflective layer pairs,forming a capping layer on the multilayer stack of reflective layers,and forming absorber layer on the capping layer, the absorber layercomprising an alloy of carbon and antimony, wherein the alloy of carbonand antimony comprises about 3.0 wt. % to about 27.1 wt. % carbon andabout 72.9 wt. % to about 97 wt. % antimony, for example, about 6.0 wt.% to about 15 wt. % carbon and about 85 wt. % to about 94 wt. %antimony, for example, about 90.6 wt. % antimony and about 9.4 wt. %carbon. In other embodiments, the alloy of carbon and antimony comprisesabout 35 wt. % to about 55 wt. % carbon and about 45 wt. % to about 65wt. % antimony, for example, about 52 wt. % carbon and about 48 wt. % toabout 55 wt. % antimony, for example, about 51.3 wt. % antimony and 48.7wt. % carbon. In one or more embodiments, the alloy of carbon andantimony is amorphous.

The EUV mask blank can have any of the characteristics of theembodiments described above with respect to FIG. 4 and FIG. 5, and themethod can be performed in the system described with respect to FIG. 3.

Thus, in an embodiment, the plurality of reflective layers are selectedfrom molybdenum (Mo) containing material and silicon (Si) containingmaterial and the absorber layer is an alloy of carbon and antimony,wherein the alloy of carbon and antimony comprises about 27.1 wt. %carbon and about 72.9 wt. % to about 97 wt. % antimony, for example,about 6.0 wt. % to about 15 wt. % carbon and about 85 wt. % to about 94wt. % antimony, for example, about 90.6 wt. % antimony and about 9.4 wt.% carbon. In other embodiments, the alloy of carbon and antimonycomprises about 35 wt. % to about 55 wt. % carbon and about 45 wt. % toabout 65 wt. % antimony, for example, about 52 wt. % carbon and about 48wt. % to about 55 wt. % antimony, for example, about 51.3 wt. % antimonyand 48.7 wt. % carbon. In one or more embodiments, the alloy of carbonand antimony is amorphous.

In another specific method embodiment, the different absorber layers areformed in a physical deposition chamber having a first cathodecomprising a first absorber material and a second cathode comprising asecond absorber material. Referring now to FIG. 6 an upper portion of amulti-cathode source chamber 500 is shown in accordance with anembodiment. The multi-cathode chamber 500 includes a base structure 501with a cylindrical body portion 502 capped by a top adapter 504. The topadapter 504 has provisions for a number of cathode sources, such ascathode sources 506, 508, 510, 512, and 514, positioned around the topadapter 504.

In one or more embodiments, the method forms an absorber layer that hasa thickness in a range of 5 nm and 60 nm. In one or more embodiments,the absorber layer has a thickness in a range of 51 nm and 57 nm. In oneor more embodiments, the materials used to form the absorber layer areselected to effect etch properties of the absorber layer. In one or moreembodiments, The alloy of the absorber layer is formed by co-sputteringan alloy absorber material formed in a physical deposition chamber,which can provide much thinner absorber layer thickness (less than 30nm) and achieving less than 2% reflectivity and desired etch properties.In an embodiment, the etch properties and other desired properties ofthe absorber layer can be tailored to specification by controlling thealloy percentage of each absorber material. In an embodiment, the alloypercentage can be precisely controlled by operating parameters suchvoltage, pressure, flow etc., of the physical vapor deposition chamber.In an embodiment, a process gas is used to further modify the materialproperties, for example, N₂ gas is used to form nitrides of carbon andantimony. The alloy absorber material can comprise an alloy of carbonand antimony which comprises about 3.0 wt. % to about 27.1 wt. % carbonand about 72.9 wt. % to about 97 wt. % antimony, for example, about 6.0wt. % to about 15 wt. % carbon and about 85 wt. % to about 94 wt. %antimony, for example, about 90.6 wt. % antimony and about 9.4 wt. %carbon. In other embodiments, the alloy of carbon and antimony comprisesabout 35 wt. % to about 55 wt. % carbon and about 45 wt. % to about 65wt. % antimony, for example, about 52 wt. % carbon and about 48 wt. % toabout 55 wt. % antimony, for example, about 51.3 wt. % antimony and 48.7wt. % carbon.

The multi-cathode source chamber 500 can be part of the system shown inFIG. 3. In an embodiment, an extreme ultraviolet (EUV) mask blankproduction system comprises a substrate handling vacuum chamber forcreating a vacuum, a substrate handling platform, in the vacuum, fortransporting a substrate loaded in the substrate handling vacuumchamber, and multiple sub-chambers, accessed by the substrate handlingplatform, for forming an EUV mask blank, including a multilayer stack ofreflective layers on the substrate, the multilayer stack including aplurality of reflective layer pairs, a capping layer on the multilayerstack of reflective layers, and an absorber layer on the capping layer,the absorber layer made from an alloy of carbon and antimony. The systemcan be used to make the EUV mask blanks shown with respect to FIG. 4 orFIG. 5 and have any of the properties described with respect to the EUVmask blanks described with respect to FIG. 4 or FIG. 5 above.

Processes may generally be stored in the memory as a software routinethat, when executed by the processor, causes the process chamber toperform processes of the present disclosure. The software routine mayalso be stored and/or executed by a second processor (not shown) that isremotely located from the hardware being controlled by the processor.Some or all of the method of the present disclosure may also beperformed in hardware. As such, the process may be implemented insoftware and executed using a computer system, in hardware as, e.g., anapplication specific integrated circuit or other type of hardwareimplementation, or as a combination of software and hardware. Thesoftware routine, when executed by the processor, transforms the generalpurpose computer into a specific purpose computer (controller) thatcontrols the chamber operation such that the processes are performed.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present disclosure without departing from the spiritand scope of the disclosure. Thus, it is intended that the presentdisclosure include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A method of manufacturing an extreme ultraviolet (EUV) mask blank comprising: forming on a substrate a multilayer stack which reflects EUV radiation, the multilayer stack comprising a plurality of reflective layer pairs; forming a capping layer on the multilayer stack; and forming an absorber layer on the capping layer, the absorber layer comprising an alloy selected from the group consisting of an alloy consisting essentially of carbon and antimony and an alloy of consisting essentially of carbon, antimony and one or more of a nitrogen dopant and an oxygen dopant.
 2. The method of claim 1, wherein the alloy of carbon and antimony comprises about 3.0 wt. % to about 27.1 wt. % carbon and about 72.9 wt. % to about 97 wt. % antimony.
 3. The method of claim 1, wherein the alloy of carbon and antimony comprises about 35 wt. % to about 55 wt. % carbon and about 45 wt. % to about 65 wt. % antimony.
 4. The method of claim 2, wherein the alloy of carbon and antimony comprises about 6.0 wt. % to about 15 wt. % carbon and about 85 wt. % to about 94 wt. % antimony.
 5. The method of claim 3, wherein the alloy of carbon and antimony comprises about 45 wt. % to about 52 wt. % carbon and about 48 wt. % to about 55 wt. % antimony.
 6. The method of claim 1, wherein the alloy is formed by co-sputtering the carbon and antimony with a gas selected from one or more of argon (Ar), oxygen (O₂), or nitrogen (N₂) to form the absorber layer.
 7. The method of claim 1, wherein the alloy is deposited layer by layer as a laminate of carbon and antimony layers using a gas selected from one or more of argon (Ar), oxygen (O₂), or nitrogen (N₂) to form the absorber layer.
 8. The method of claim 1, wherein the alloy is deposited using a bulk target having the same composition as the alloy and is sputtered using a gas selected from one or more of argon (Ar), oxygen (O₂), or nitrogen (N₂) to form the absorber layer.
 9. The method of claim 2, wherein the alloy of carbon and antimony is doped with one of more of nitrogen or oxygen in a range of from 0.1 wt. % to 5 wt. %.
 10. The method of claim 3, wherein the alloy of carbon and antimony is doped with one of more of nitrogen or oxygen in a range of from about 0.1 wt. % to about 5 wt. %.
 11. An extreme ultraviolet (EUV) mask blank comprising: a substrate; a multilayer stack which reflects EUV radiation, the multilayer stack comprising a plurality of reflective layer pairs; a capping layer on the multilayer stack of reflecting layers; and an absorber layer comprising an alloy selected from the group consisting of an alloy consisting essentially of carbon and antimony and an alloy consisting essentially of carbon, antimony and one or more of a nitrogen dopant and an oxygen dopant.
 12. The extreme ultraviolet (EUV) mask blank of claim 11, wherein the alloy of carbon and antimony comprises about 3.0 wt. % to about 27.1 wt. % carbon and about 72.9 wt. % to about 97 wt. % antimony.
 13. The extreme ultraviolet (EUV) mask blank of claim 11, the alloy of carbon and antimony comprises about 35 wt. % to about 55 wt. % carbon and about 45 wt. % to about 65 wt. % antimony.
 14. The extreme ultraviolet (EUV) mask blank of claim 12, wherein the alloy of carbon and antimony comprises about 6.0 wt. % to about 15 wt. % carbon and about 85 wt. % to about 94 wt. % antimony.
 15. The extreme ultraviolet (EUV) mask blank of claim 13, wherein the alloy of carbon and antimony comprises about 45 wt. % to about 52 wt. % carbon and about 48 wt. % to about 55 wt. % antimony.
 16. The extreme ultraviolet (EUV) mask blank of claim 11, wherein the absorber layer has a thickness of less than 45 nm.
 17. The extreme ultraviolet (EUV) mask blank of claim 11, wherein the absorber layer further comprises a range of rom about 0.1 wt. % to about 5 wt. % of a dopant selected from one or more of nitrogen or oxygen.
 18. The extreme ultraviolet (EUV) mask blank of claim 11, wherein the absorber layer has a thickness of less than 45 nm.
 19. The extreme ultraviolet (EUV) mask blank of claim 11, wherein the absorber layer is etch selective relative to the capping layer.
 20. An extreme ultraviolet (EUV) mask blank comprising: a substrate; a multilayer stack which reflects EUV radiation, the multilayer stack comprising a plurality of reflective layer pairs including molybdenum (Mo) and silicon (Si); a capping layer on the multilayer stack of reflecting layers; and an absorber layer comprising an alloy selected from the group consisting of an alloy consisting essentially of carbon and antimony and an alloy of carbon and antimony optionally doped with one or more of nitrogen and oxygen. 